The purpose of this proposal is to elucidate basic mechanisms of platelet lipid metabolism, to examine control mechanisms which regulate platelet plug formation, and to study alterations in platelet lipids which are associated with disorders of platelet function that cause hemorrhage or thrombosis. We plan to achieve these goals by studying: 1) thrombin-induced alterations in phospholipid metabolism of the intact platelet and of the isolated plasma membrane of the platelet, and: 2) pathways of arachidonic acid metabolism and prostaglandin formation in normal platelets and in platelets obtained from patients with hereditary and acquired disorders of platelet function. This research is of direct relevance to an understanding of the participation of platelets in arterial and venous thrombosis, major causes of mortality and disability in our society.